Self-adjusting hot box

ABSTRACT

A self-adjusting hot box includes a box ( 1 ) with a fan, a heater ( 50 ) placed in the box ( 1 ), a thermostat ( 30 ) and a power supply ( 20 ) applied to provide power to the fan ( 12 ), the thermostat ( 30 ) and the heater ( 50 ). The heater ( 50 ) includes a plurality of heat generating devices, and each of the heat generating devices includes a plurality of power resistors ( 60 ) in electrical parallel connection. The thermostat ( 30 ) includes a T type thermocouple ( 33 ) disposed in the box ( 1 ), a double-acting relay ( 37 ), a temperature controller ( 32 ) and a plurality of single-acting relays. The power supply ( 20 ) includes a transformer ( 21 ), a bridge clipper diode ( 23 ) and a capacitor ( 25 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hot box, and more particularly to a self-adjusting hot box for testing a hot property of an electrical device.

2. Background of the Invention

Hot property is a sort of important properties for an electrical device such as computer, sever, notebook and so on. Hot property reflects an operation state of the electrical device in a different temperature environment. When hot property of an electrical device is tested, a kind of simulation temperature environment is needed. Traditionally, a hot box is designed for testing an electrical device placed therein. The temperature in the hot box can be adjusted within a range of necessary temperature. Consequently, the hot box provides a kind of simulation temperature environment for testing the electrical device.

In fact, the electrical device is placed in natural convection environment and temperature of every part of the electrical device is approximately uniform. However, if the hot box cannot simulate a real temperature environment, the test for hot property of the electrical device is no effect. Understandably, some attempts have been taken to introduce an improved hot box.

What is needed, therefore, is a self-adjusting hot box that can simulate a real temperature environment for testing an electrical device.

SUMMARY

A self-adjusting hot box includes a box with a fan, a heater placed in the box, a thermostat and a power supply applied to provide power to the fan, the thermostat and the heater. The heater includes a plurality of heat generating devices, and each heat generating device includes a plurality of power resistors in electrical parallel connection. The thermostat includes a T type thermocouple disposed in the box, a double-acting relay, a temperature controller and a plurality of single-acting relays. The power supply includes a transformer, a bridge clipper diode and a capacitor. The T type thermocouple measures temperature in the box 1 and transfers the temperature to the temperature controller. The temperature controller and the relays jointly control the fan and the heater. The fan starts to operate and the heater is cut off when the temperature is higher than the testing temperature. The fan is cut off and the heater is out of service when the temperature is lower than the testing temperature. Therefore, the testing temperature is maintained. In addition, the heat that the power resistors generate is a mixture of emanation heat and radiation heat, thereby solving a problem that the heat is non-uniformly distributed. The heat in the box is free convection, thereby simulating the natural environment.

Other advantages and novel features of the present invention will be drawn from the following detailed description of preferred embodiment of the present invention with the attached drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a self-adjusting hot box in accordance with a preferred embodiment of the present invention including a box with a door, a power supply, a thermostat and a heater;

FIG. 2 is similar to FIG. 1, but the door being open;

FIG. 3 is a functional block diagram of the self-adjusting hot box;

FIG. 4 is a fragmentary schematic diagram of the power supply and the thermostat as shown in FIG. 3; and

FIG. 5 is a fragmentary schematic diagram of the heater as shown in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a self-adjusting hot box in accordance with a preferred embodiment of the present invention includes a box 1 and a door 2 pivotably mounted to the box 1. A middle portion of the door 2 forms a transparent glass window 3 for observing the interior of the box 1 conveniently. A handle 4 is formed on the door 2 for opening the door 2 easily. Each sidewall of the box 1 defines a recess 6 for carrying the box 1 conveniently. An opening 7 is defined in a middle portion of a top panel of the box 1, and a fan 12 is mounted in the opening 7.

Referring to FIG. 2, a supporting board 10 is net-shaped and disposed in the box 1 for supporting an electrical component.

Referring to FIG. 3, the self-adjusting hot box can adjust temperature automatically by a control circuit. The control circuit of the self-adjusting hot box includes a power supply 20, a thermostat 30 and a heater 50.

Referring to FIG. 4, the power supply 20 includes a transformer 21, a bridge clipper diode 23 and a capacitor 25. An input terminal of the supply power 20 is input AC of 220V. An output terminal of transformer 21 is connected with an input terminal of the bridge clipper diode 23. An output terminal of the bridge clipper diode 23 is connected in electrical parallel with the capacitor 25 to serve as a power output terminal 27 of the power supply 20. After transformation of the transformer 21, rectification of the bridge clipper diode 23 and the capacitor 25, the power output terminal 27 of the power supply 20 outputs DC of 12V that provides power to the fan 12 and heater 50.

The thermostat 30 includes a temperature controller 32, a T type thermocouple 33, a double-acting relay 37 and a plurality of single-acting relays 41, 43, 45, 47 in electrical parallel connection. The T type thermostat 33 is connected with the temperature controller 32. The temperature controller 32 is input AC of 220V, and the temperature controller 32 includes a pilot switch 35 connected with the double-acting relay 37. The double-acting relay 37 includes a first key 371 and a second key 372. One terminal of the first key 371 is connected with the power output terminal 27, and the other terminal of the first key 371 is connected with the fan 12, thereby controlling operation of the fan 12. One terminal of the second key 372 is connected with the power output terminal 27, and the other terminal of the second key 372 is connected with the single-acting relays 41, 43, 45, 47. The single-acting relays 41, 43, 45, 47 include switches 42, 44, 46, 48 respectively. Terminals of the switches 42, 44, 46, 48 are respectively connected with the power output terminal 27, and the other terminals of the switches 42, 44, 46, 48 are respectively K1, K2, K3, K4.

Referring also to FIG. 5, the heater 50 includes a plurality of heat generating devices 51, 53, 55, 57 and a plurality of single-acting relays 41, 43, 45, 47 corresponding to the heat generating devices 51, 53, 55, 57. Each of the heat generating devices 51, 53, 55, 57 includes a plurality of power resistors 60 and diodes 52, 54, 56, 58 in electrical parallel connection. One terminal of the heat generating devices 51, 53, 55, 57 and anodes of the diodes 52, 54, 56, 58 are coupled to the output terminals K1, K2, K3, K4 of the single-acting relays 41, 43, 45, 47, and the other terminal of the heat generating devices 51, 53, 55, 57 and anodes of the diodes 52, 54, 56, 58 are coupled to the grounding.

The T type thermocouple 33 is disposed in the box 1 for testing the temperature accurately. The heat generating devices 51, 53, 55, 57 of the heater are placed and distributed uniformly at a bottom of the box 1 for free convection heat transfer. The other components of the control circuit are placed in a control circuit box (not shown). The control circuit box can be placed everywhere. However, the control circuit box may as well be placed outside the box 1 in view of avoiding engendering temperature error in the box 1.

In use of the self-adjusting hot box, the electrical device is placed on the supporting board 10 and then the door 2 is closed. The temperature controller 32 is set to a testing temperature that is needed. The T type thermocouple 33 measures a temperature in the box 1 and transfers the temperature signal to the temperature controller 32. When the temperature is higher than the testing temperature, the temperature controller 32 cuts off the pilot switch 35 automatically. Therefore, the double-acting relay 37 controlled by the pilot switch 35 switches on the first key 371 and cuts off the second key 372 automatically. The single-acting relays 41, 43, 45, 47 connected with the first key 371 are cut off with the power output terminal 27, and the heater 50 is also switched off. Simultaneously, the first key 371 is electrically connected with the power output terminal 27, and the fan 12 is turned on so that the temperature in the box 1 is reduced. On the contrary, when the temperature is lower than the testing temperature, the temperature controller 32 switches on the pilot switch 35 automatically. Accordingly, the double-acting relay 37 controlled by the pilot controller 35 cuts off the first key 371 and switches on the second key 372 automatically so that the fan 12 is cut off and is out of service. Simultaneously, after the second key 372 is switched on, the switches 42, 44, 46, 48 of the single-double relays 41, 43, 45, 47 are switched on, and the output terminals K1, K2, K3, K4 are electrically connected with the power output terminal 27. Consequently, the diodes 52, 54, 56, 58 of the heat generating devices 51, 53, 55, 57 are electrified and the power resistors 60 start to operate and generate heat. The heat that the power resistor 60 generates is a mixture of emanation heat and radiation heat, thereby solving a problem that the heat is non-uniformly distributed. In addition, the heat in the box 1 is free convection, thereby simulating the natural environment.

Alternatively, the T type thermocouple 33 can be replaced by other temperature sensors. In order to lower temperature rapidly, more fans are needed. The number of heat generating device can be decreased and increased in light of factual situation.

While the present invention has been illustrated by the description of preferred embodiment thereof, and while the preferred embodiment has been described in considerable details, it is not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications within the spirit and scope of the present invention will readily appear to those skilled in the art. Therefore, the present invention is not limited to the specific details and illustrative example shown and described. 

1. A self-adjusting hot box comprising: a box having a supporting board disposed therein and a fan therein; a heater placed in the box; a thermostat electrically connected with the heater for controlling operation of the fan and the heater alternately; and a power supply for providing power to the thermostat and the heater.
 2. The self-adjusting hot box as recited in claim 1, wherein the heater comprises a plurality of heat generating devices, and each heat generating device comprises a plurality of power resistors in electrical parallel connection.
 3. The self-adjusting hot box as recited in claim 2, wherein each of the heat generating devices of the heater further comprises a diode in electrical parallel connection with the power resistors.
 4. The self-adjusting hot box as recited in claim 1, wherein the power supply comprises: a transformer; a bridge clipper diode; and a capacitor; wherein an input terminal of the transformer is input AC of 220V, an output terminal of the transformer is electrically connected with an input terminal of the bridge clipper diode, an output terminal of the bridge clipper diode is in electrical parallel connection with the capacitor, and a power output terminal of the power supply is connected with the capacitor and the bridge clipper diode.
 5. The self-adjusting hot box as recited in claim 1, wherein the thermostat comprises a temperature sensor disposed in the box, a double-acting relay and a temperature controller coupled with the temperature sensor and the double-acting relay.
 6. The self-adjusting hot box as recited in claim 5, wherein the temperature controller further comprises a pilot switch connected with the double-acting relay.
 7. The self-adjusting hot box as recited in claim 5, wherein the double-acting relay comprises a first key and a second key, the second key is switched on when the first key is cut off, the first key is switched on when the second key is cut off.
 8. The self-adjusting hot box as recited in claim 7, wherein a single-acting relay is connected with each heat generating device of the heater, the single-acting relay is connected with one terminal of the second key of the double-acting relay, and the other terminal of the second key is connected with the power output terminal of the power supply.
 9. The self-adjusting hot box as recited in claim 1, wherein the supporting board is net-shaped.
 10. The self-adjusting hot box as recited in claim 1, wherein a door with a handle is attached to the box, a middle portion of the door forms a transparent glass window.
 11. The self-adjusting hot box as recited in claim 1, wherein an opening is defined in the box, and the fan is received in the opening and connected with the thermostat.
 12. A self-adjusting hot box for testing hot property of an electrical component comprising: a box having a supporting board disposed therein; a heater placed in the box for heating the electrical component; a thermostat electrically connecting the heater for controlling operation of the heater; and a power supply for providing power to the thermostat and the heater.
 13. The self-adjusting hot box as recited in claim 12, wherein the heater comprises a plurality of heat generating devices, and each heat generating device comprises a plurality of power resistors and a diode in electrical parallel connection.
 14. The self-adjusting hot box as recited in claim 12, wherein the power supply comprises: a transformer; a bridge clipper diode; and a capacitor; wherein an input terminal of the transformer is set to be AC of 220V, an output terminal of the transformer is electrically connected with an input terminal of the bridge clipper diode, an output terminal of the bridge clipper diode is in electrical parallel connection with the capacitor, and a power output terminal of the power supply is connected with the capacitor and the bridge clipper diode.
 15. The self-adjusting hot box as recited in claim 12, wherein the thermostat comprises a temperature sensor disposed in the box, a double-acting relay and a temperature controller coupled with the temperature sensor and the double-acting relay.
 16. The self-adjusting hot box as recited in claim 15, wherein the temperature controller further comprises a pilot switch connected with the double-acting relay.
 17. The self-adjusting hot box as recited in claim 15, wherein the double-acting relay comprises a first key and a second key, the second key is switched on when the first key is cut off, the first key is switched on when the second key is cut off.
 18. The self-adjusting hot box as recited in claim 17, wherein a single-acting relay is connected with each heat generating device of the heater, the single-acting relay is connected with one terminal of the second key of the double-acting relay, and the other terminal of the second key is connected with the power output terminal of the power supply.
 19. A method to establish a thermal test environment for an electrical device, comprising the steps of: preparing a box with a temperature-controllable space therein; equipping said box with a heater capable of raising temperature of said space; ventilating said space of said box with an outside of said box; and controlling said temperature of said space of said box by means of said heater and said ventilating step.
 20. The method as recited in claim 19, wherein a fan is equipped on said box to communicate said space with said outside of said box and perform said ventilating step. 